SNCA and Parkinson disease: Mechanistically, the pathogenesis of PD is underlined by oxidative and nitrosative stress [20]; misfolding and aggregation of proteins, particularly alpha synuclein [21]; mitochondrial dysfunction; neuroinflammation [22]; and dysbiosis of gut microbiota [23], all of which work synergistically, leading to the death of DA neurons and the occurrence of PD [24] (Figure 1).